Metering pumps and similar apparatuses for metering and feeding out different types of fluid materials can require cleaning in order to remove material which has been deposited on components in the pump or in order to prepare the pump for feeding out another material. It is desirable to be able to clean the metering pump without it needing to be dismantled, with a view to saving time and being able to carry out rapid changes of material.
U.S. Pat. No. 4,759,695 discloses an example of an arrangement for in situ cleaning of a metering pump. This pump comprises an inlet, an outlet and an intervening rotatable valve. Material is fed in and out by the action of a cylinder, the piston of which faces an opening in the valve. A cone-shaped front part of the valve bears sealingly against an interacting conical seat in the valve-facing end of the cylinder. In a first position, the valve is open towards the inlet, the piston being actuated to suck material into the cylinder from the inlet. After this, the valve is rotated into a second position, in which the piston can force the material out through the outlet. When the pump is to be cleaned, the cone-shaped section of the valve is drawn out of engagement with the conical seat with a view to achieving a direct connection between inlet and outlet. A cleaning liquid can hereupon be flushed through the metering pump for cleaning of the valve. One problem with this solution is that material residues can be left, since the through-flow substantially passes by the front section of the valve.
U.S. Pat. No. 4,842,026 discloses a further example of an arrangement for in situ cleaning of a metering pump. This pump has a similar structure, having a rotatable valve and a piston-cylinder device for the feed-in and feed-out of material. In connection with the cleaning, cleaning liquid is flushed firstly through a nozzle in the inlet and secondly towards an inner end face of the valve via a separate nozzle. During the cleaning, the valve can also be rotated for the removal of further material. This arrangement, too, creates problems with left-over material residues, since the flow from the said nozzles does not reach the whole of the space which is to be cleaned.
The object of the invention is to provide a method for achieving more effective and faster cleaning of a metering pump and an arrangement for implementing the method. The invention also relates to an improved arrangement which allows in situ cleaning of all the components incorporated in the metering pump, without these needing to be disassembled.